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I took great delight in singing a song about watermelons to my son when he was a toddler. And I have great memories from my own childhood of eating watermelon outside on the grass on hot summer days. Looking back, I’m sure this alfresco eating approach was a mess-minimisation measure from my mum, but it did add to the overall fun of it. I recall juices dripping down my arms, competitions to see who could spit seeds the furthest (seedless watermelon varieties have spoiled this) and washing up with the garden hose afterwards. Watermelon is beautifully sweet and an amazing colour (from the lycopene antioxidant content), as well as a source of vitamin C. However, there’s a cloud over its image – it is believed to be “high in sugar” and have a high GI. People with diabetes are warned to take care. Let’s unpack this.

Watermelon, like other fruits, contains natural sugars. That’s why they taste so great and why they’re so good at providing energy and hydration. Watermelon is not especially high in its natural sugars content, coming in at around 7% (7g per 100g). The high moisture content of around 92% dilutes the sugars considerably and makes it quite filling. Other fruits come in way higher such as mango or banana (13% sugars), red grapes (16%) or pear (12%). And that’s not to say these fruits are unhealthy or too sweet, just that watermelon isn’t “high in sugar”. There’s nothing unhealthy about natural sugars consumed in whole fruit.
The Glycemic Index (GI) story is more complex. In previous GI tables, watermelon has been listed as having a high GI (76), and we know high GI foods require care with their consumption as they may raise blood glucose levels, especially in people with diabetes. However, the Glycemic Load (GL) tells a different story. Remember, the GL is a measure of the glycemic impact of a serving of the food, or the amount you eat. At a serving size of 120g (about two thin slices of ¼ of a circle edge each) the GL of watermelon is ~6 (low). And even doubling this amount to four slices (easy-to-do because it’s so delicious) the GL is 13, which is still medium, not high.

But wait, there’s more. The latest Glycemic Index tables published in 2021, show that watermelon has a low GI of 50, based on an average of four varieties. Now it must be said the varieties tested were from Malaysia and there may be some differences between countries, however, I like to think the new data is good news for watermelon lovers. With an average GI of 50, watermelon has a GL of 4 (low) for a 120g portion and 9 (still low) for a larger 240g portion.
So, any way you slice and dice it, watermelon is fine to eat for everyone. And another plus is it is so high in water that it fills you up making it difficult to overeat – a little gift from Mother Nature for greedy guts’ like me.

Enjoy watermelon just as it is, in a fruit salad, frozen for a cooling summer treat, pureed into a slushie and in juice cocktails/mocktails. You can also get all exotic and use it in unexpected ways such as in a salad with feta and mint or prawns and watercress, or indulge in a watermelon cake, trifle or panna cotta.

Read more:

4.5 Health Stars  
Glycemic index average of 50  
Serving size – 2 thin slices (120 g or 4.25 oz)  
Kilojoules 160
Calories 38
Protein (g) 0.72
Fats (g) – total 0.0
Includes: – Saturated fat (g) 0.0
– Monounsaturated fat (g) 0.0
– Polyunsaturated fat (g) 0.0
Saturated : unsaturated fat ratio N/a
Carbohydrates (g) – Total 9.3
Available (Includes): 8.8
–Natural sugars (g) 8.4
–Natural starches (g) 0.4
–Added sugars (g) 0.0
–Added starches (g) 0.0
Unavailable (Includes): 0.5
–Dietary fibre (g) 0.5
Sodium (mg) 4
Glycemic load (g) 4.4
Diabetes exchanges 0.5
Ingredients: watermelon  
Source: International tables of glycemic index and glycemic load values, 2021

Nicole Senior is an Accredited Practising Dietitian, author, consultant, cook and food enthusiast who strives to make sense of nutrition science and delights in making healthy food delicious.

Contact: You can follow her on Twitter, Facebook, Pinterest, Instagram or check out her website